had of (had)

Many people write or type "should of" because spoken "should've" sounds the same. The correct forms are "should have" (formal) or "should've" (informal). "Of" is a preposition and cannot replace the auxiliary "have."

Quick answer

Never write "should of." Use "should have" for formal writing or "should've" when mimicking speech. "Should of" is a phonetic error, not a grammatical form.

"I should have left earlier." = correct
"I should've left earlier." = informal, acceptable
"I should of left earlier." = incorrect

Core grammar: why have (not of)

Modals (should, could, would, might) form the perfect with have + past participle: modal + have + past participle. That structure expresses an action completed before another time.

Structure: subject + modal + have + past participle - e.g., "She should have gone."
"Of" is a preposition; it does not create the perfect aspect and cannot replace "have."

Wrong → Right: Wrong: I should of finished the report. -
Right: I should have finished the report.
Wrong → Right: Wrong: She should of told us. -
Right: She should have told us.

Real usage and tone: should have vs should've

Choose the full form for formal contexts and the contraction for casual ones. Avoid "should of" in every context.

Formal: use "should have" (essays, reports, job applications).
Informal: "should've" is fine for texts, chats, and speech-like writing.
Never: "should of" or "shouldve" (missing apostrophe).

Formal: I should have completed the analysis before the meeting.
Informal: I should've told you - sorry!

Examples: wrong → right lists (work, school, casual)

Common wrong forms paired with corrected sentences for quick copy-paste use.

Work:
Wrong: I should of included the spreadsheet in the presentation. -
Right: I should have included the spreadsheet in the presentation.
Work:
Wrong: We should of asked for clarification before approving. -
Right: We should have asked for clarification before approving.
Work:
Wrong: I should of scheduled that meeting earlier. -
Right: I should have scheduled that meeting earlier.
School:
Wrong: I should of cited more sources in the literature review. -
Right: I should have cited more sources in the literature review.
School:
Wrong: The student should of included more data. -
Right: The student should have included more data.
School:
Wrong: I should of revised my thesis statement. -
Right: I should have revised my thesis statement.
Casual:
Wrong: I should of brought a jacket - it's freezing. -
Right: I should've brought a jacket - it's freezing.
Casual:
Wrong: You should of told me you were running late. -
Right: You should have told me you were running late.
Casual:
Wrong: He should of apologized. -
Right: He should've apologized.

Quick diagnostic checklist (fix a sentence in 30 seconds)

Read the sentence aloud. If it sounds like "of," swap to "have" and hear whether the sentence flows.
Confirm structure: modal + have + correct past participle (gone, written, eaten, seen).
Decide tone: use "should have" for formal, "should've" for informal.
Scan for missing apostrophes ("shouldve") and wrong participles ("should have went" → "should have gone").

Diagnostic: Sentence: We should of left earlier. → Say: "We should have left earlier." Replace and proofread.
Diagnostic: Sentence: She should of known about the policy. → Swap to: "She should have known about the policy."

Try your own sentence

Test the whole sentence rather than the isolated phrase. Context usually makes the correct form obvious.

Hyphenation, contractions and spacing: common typographic traps

Watch for three frequent typing mistakes:

Missing apostrophe in contractions: should've is correct; shouldve is not.
Auto-correct or predictive text may suggest "should of" when you meant "should've."
Copy-pasting informal, spoken text can carry the "of" error into formal drafts.

Wrong → Right: Wrong: Shouldve told you sooner. -
Right: Should've told you sooner.
Wrong → Right: Wrong: I should of known better. -
Right: I should've known better.

Memory trick: short checks to stop the habit

These quick tests help fix the habit when you write or proofread.

Swap test: If "should have" sounds natural when you read aloud, write "have."
Apostrophe test: Want a contraction? Always add the apostrophe: "should've."
30-second drill: Search a recent message for "of" errors, replace with "have" or " 've," and repeat until automatic.

Mnemonic: Hear "should of" → think "have." Hear "should've" → write "should've."

Similar mistakes and participle pitfalls

The same mishearing affects could/would/might and can hide incorrect participles after have.

Wrong-word pattern: could of → could have; would of → would have; might of → might have; had of → had (or had + past participle depending on tense).
Check the past participle after correcting "have": use "gone," "written," "eaten," not "went," "wrote," "ate."

Wrong → Right: Wrong: We could of arrived earlier. -
Right: We could have arrived earlier.
Wrong → Right: Wrong: She would of helped if she could. -
Right: She would have helped if she could.
Wrong → Right: Wrong: I should have went to the dentist. -
Right: I should have gone to the dentist.
Wrong → Right: Wrong: I had of known. -
Right: I had known.

Rewrite help: ready-to-use templates and common fixes

Quick templates to replace incorrect forms. Check the participle when you rewrite.

Template: Subject + should have + [past participle] (formal) | Subject + should've + [past participle] (informal).
Typical participles to watch for: gone, done, seen, known, written, eaten.

Rewrite: I should of responded sooner → I should have responded sooner.
Rewrite: We should of left earlier → We should have left earlier / We should've left earlier (informal).
Rewrite: You should of known about the policy → You should have known about the policy.
Rewrite for feedback: They should of checked the sources → They should have checked the sources.

FAQ

Is "I should of" ever correct?

No. "I should of" is nonstandard. Use "I should have" (formal) or "I should've" (informal).

Why do people write "should of" instead of "should've"?

Because "should've" sounds like "should of" in speech. Writing must reflect the auxiliary "have," not the preposition "of."

Should I use "should've" in an essay or business email?

Avoid contractions in formal writing. Use "should have" in essays, reports, and professional emails. Reserve "should've" for informal contexts.

How do I fix a sentence that uses this mistake?

Read the sentence aloud, replace any "of" you hear with "have," ensure the modal + have + correct past participle structure, then choose the appropriate tone.

What other phrases make the same mistake?

Watch for "could of," "would of," "might of," and participle errors such as "should have went" (correct: "should have gone").

Want to check a sentence now?

Paste a sentence into your draft, run the quick checklist above, and replace "of" with "have" where appropriate. Repeating the correction trains the ear and stops the habit.